New thiazoline and thiazole accelerators



NEW THIAZOLINE AND THIAZOLE ACCELERATORS Richard Leshin, Akron, Ohio,assignor to The Goodyear Tire & Rubber Company, Akron, Ohio, acorporation of Ohio N0 Drawing. Application August 4, 1955 Serial No.526,564

18 Claims. (Cl. 260--79.5)

This invention relates to the vulcanization of rubber. More particularlythis invention relates to new compounds which are accelerators ofvulcanization of rubber.

It is an object of this invention to provide rapid vulcanization ofrubber while avoiding scorching. It is another object to provideimproved compositions for vulcanizing, rubber. It is another object toprovide a new class of compounds which accelerate the vulcanization ofrubber. Other objects will appear hereinafter as the description of theinvention proceeds.

According to this invention the acceleration of the vulcanization ofrubber with sulfur is produced by heating rubber and sulfur in thepresence of an ester of a compound of the general formula HOOC- ArSS-Tin which Ar is an arylene radical, and T represents a thiazolyl orthiazolinyl radical. These compounds are esters of carboxy arylenedithio thiazoles and carboxy arylene dithio thiazolines.

The accelerators of this invention can be prepared by reacting a sodiumor potassium salt of a Z-mercaptothiazole or a sodium or potassium saltof a 2-mercaptothiazoline with an ester of a carboxy arylene sulfenylchloride.

The sulfenyl chloride may conveniently be prepared by passing drychlorine into a suspension or slurry of an ester of a bis(carboxyarylene) disulfide as illustrated in Example 1 below in whicho,o'-dimethyl dithiodibenzoate is used as a representative startingmaterial.

EXAMPLE 1 Chlorine gas was passed over a suspension of 33.5 grams ofo,o'-dimethyl dithiodibenzoate in 250 milliliters of benzene, withoccasional shaking. When 10 grams had been absorbed, the chlorine wasdisconnected, and the reaction mixture was allowed to stand over nightunder a calcium chloride drying tube. The resultant sollution was thenvacuum-distilled until there. was no more chlorine in the distillate.The volume of the residue was 136 milliliters, and contained 0.2 mol ofo-carbomethoxybenzenesulfenyl chloride.

Example 2 illustrates the preparation of a representative compound ofthis invention.

EXAMPLE 2 A benzene solution containing 0.1 mol ofo-carbo1nethoxybenzenesulfenyl chloride prepared by the method ofExample 1 above was slowly added to a filtered solution of 0.1 mol ofthe sodium salt of 2-mercaptobenzothiazole dissolved in 75 millilitersof water. The solutions were stirred while being mixed together andagitation was continued for 15 minutes after all of the sulfenylchloride had been added. The benzene layer was separated from theaqueous layer, transferred to a distilling flask and the benzene wasdistilled off under vacuum. The residual black oil was triturated withalcohol. The product solidified and was washed and dried. Afterrecrystallization it had a melting point of 86 to 87 C., and on analysiswas found to contain 28.43% of sulfur and 4.20% of nitrogen. Thetheoretical sulfur and nitrogen contents of 2-(0- 2,866,778 PatentedDec. 30, 1958 carbomethoxyphenyldithio)-benzothiazole are 28.85% and4.20% respectively.

Other accelerators of this invention, i. e. esters of compounds havingthe general formula HOOCArS-ST in which Ar-is an arylene radical and Trepresents a thiazolyl or thiazolinyl radical, can be prepared in asimilar manner by appropriate selection of starting materials. While thephenylene compounds constitute a preferred class, Ar may be any otherarylene radical such as the various, naphthylene radicals. In additionto the parent compounds, various substituted compounds containingsubstituents on the arylene, thiazole and thiazoline rings can also beused. The dithio group can be ortho, meta or para to the ester group.Various esters can be used, in-' cluding aliphatic, aromatic, aralkyl,cycloaliphatic and other esters. Representative examples are methyl,ethyl,

propyl, butyl, secondary butyl, amyl isoamyl, octyl, 2-et'hylhexyl,beta-chloroethyl, beta-cyanoethyl, beta-butoxyethyl, cyclohexyl, benzyl,phenyl, tolyl, chlorophenyl, nitrophenyl and methoxyphenyl esters. Thealkyl esters. constitute a preferred class. Representative examples ofthiazolyl radicals are 2-thiazolyl, 4,S-dimethyl-Z-thiazolyl,4,5-diethyl-2-thiazolyl, 4-methyl-2-thiazolyl, 4-ethyl-2-thiazolyl, 4butyl 2 thiazolyl, 5 ethyl 2 thiazolyl, 4 phenyl 2 thiazolyl, 2benzothiazolyl, 2 naphthothiazolyl, 6-chloro-2-benzothiazolyl,4-ethoxy-2-benzothiazolyl, 6-phenyl-2-benzothiazolyl,6-nitro-2-benzothiazolyl, 4-methyl-2-benzothiazolyl,5-ethyl-2-benzothiazo' lyl, and 6-tertiarybutyl-2-benzothiazolyl.Representative examples of thiazolinyl radicals are 2-thiazolinyl,4-methyl-2-thiazolinyl, 4,4-dimethyl-2-thiazo1inyl, 4,5-dimethyl-Z-thiazolinyl, 5-phenyl-2-thiazolinyl and 4-ethyl-2-thiazolinyl.

Further representative compounds are 2-(o-carbomethoxyphenyl-dithio)-benzothiazole, 2- o-carbethoxypheriyldithio -benzothiazole, 2- B-u-carbomethoxynaphthyl dithio] -benzothiazole, 2-o-carbomethoxy-p-chlorophenyldithio) -benzothiazole, 2-o-carbisopropoxyphenyldithio benzothiazole, 2 [o carbo (,8 chloroethoxy)phenyldithio] benzothiazole, 2 [o carbo (,8 cyanoethoxy)- phenyldithio]benzothiazole, 2 [o carbo (6 butoxyethoxy) phenyldithiol benzothiazole,2- o-carbophenoxyphenyldithio) benzothiazole, 2 (ocarbethoxyphenyldithio)-6-chlorobenzothiazole,2-(o-carbethoxy-p-chlorophenyldithio)-6-chlorobenzothiazole,2-(o-carbomethoxyphenyldithio -thiazole, 2- o-carbophenoxyphenyldithio)thiazole, 2- o-carbomethoxyphenyldithio -4,5-dimethylthiazole, 2-o-carbethoxyphenyldithio) -4-phenylthiazole,2-(o-carbopropoxyphenyldithio)-4,5-dimethylthiazole, 2-(o-carbo-secondary butoxyphenyldithio)-4,5-dimethylthiazole, 2-[o-carbo-(fl-chloroethoxy) phenyldithio] -4,5-dimethylthiazole, 2-[o-carbo-(B-cyanoethoxy)phenyldithio] 4,5 -dimethylthiazole, 2- [o-carbo(fl-butoxyethoxy) phenyldithio]-4,5-dimethylthiazole,2-(o-carbophenoxyphenyldithio)-4,5-dirnethylthiazole,2-(o-carbophenoxyphenyldithio)-4-phenylthiazole,2-(o-carbomethoxyphenyldithio)- thiazoline, 2-[fl-(a-carbomethoxynaphthyl)dithio]-thiazoline,2-(o-carbomethoxy-p-chlorophenyldithio)-6-chlorothiazoline,2-(carbisopropoxyphenyldithio)-thiazoline, 2-(o-carbophenoxyphenyldithio)-thiazoline, and2-(o-carbop-toloxyphenyldithio)-4-ethylthiazoline. The correspondingmeta and para compounds can also be used.

The eflicacy of the compounds in the vulcanization of rubber isillustrated by the following examples, employing representativecompounds of the invention in comparison with the commercial acceleratorN-oxydiethylene-Z-behzothiazolesulfenamide in a standard test recipe.The test recipe is shown as Table 1 below in which the parts are partsby weight. The ingredients were mixed on a small two-roll laboratorymill according to usual compounding procedure.

Table 1 Stock No.

A B C D Smoked sheet--. 100 100 100 100 50 50 50 50 .0 3.0 3.0 3.0 .05.0 5.0 5.0 .0 3.0 3.0 3.0 .5 2. 2. 5 2. 5 Antioxlda 1.0 1.0 1.0 1.0Nigxydlethylene-2-benzothiazole-sullenam 0 45 e 2(ooarbomethoxyphenyldithlo) benzothb run a 2(tlan-carbethoxyphenyldithlo) benzothiam 2 (o-earbomethoxyphnyldlthi0)thlaztiline- 1. 3

Samples of the above stocks were cured at 275 F. and tested for tensilestrength. and formodulus at 300% elongation. The physical properties arelisted in Table 2 below:

Table 2 Ultimate Tensile Strength in PoundsPer Square Luch The compoundsof this invention are effective accelerators of vulcanization of rubberand stocks containing these accelerators have good resistance toscorching. In addition, the compounds of this invention have goodchemical stability. This is particularly advantageous when theaccelerator is likely to be stored for some time before it is used.

The invention has been illustrated above with respect to the use of thecompounds of this invention as accelerators ofivulcanization of naturalrubber. They can also be used to accelerate the vulcanization ofsynthetic rubbers; Representative examples of such synthetic rubbers arepolybutadiene, polyisoprene, the rubbery butadiene-acrylonitrilecopolymers, rubbery butadicne-isobutylene copolymers, rubberybutadiene-styrene copolymers, rubbery butadicne-vinylpyridinecopolymers, and various other rubbery copolymers of diene hydrocarbonswith another monomer copolymerizable therewith.

The amount of accelerator and the curing conditions used in the examplesare shown for purposes of illustration, The curing conditions can bevaried over the usual range used in the sulfur vulcanization of rubber.The other compounding ingredients also can be varied and other materialssuch as pigments, plasticizers, extenders, oils and waxes can alsobe'incorporated in the compositions.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

I claim:

1. The method which comprises heating a rubber selected from the groupconsisting of natural rubber, polybutadiene, polyisoprene and rubberycopolymers of dicne hydrocarbons with another monomer copolymerizabletherewith and sulfur in the presence of an ester selected from the groupconsisting of aliphatic esters, aromatic esters, aralkyl esters andcycloaliphatic esters of a compound having the general formulaHOOC-Ar-S-S-T in which Ar is an arylene radical and T is selected fromthe group consisting of Z-thiazolyl and Z-thiazolinyl radicals.

2. The methodof claim 1 in which the arylene group is phenylene and thedithio group is in the position ortho .to the ester group.

3. The method of claim 2 in which T is Z-benzothiazolyl.

4. The method of claim 3 in which the ester is the methyl ester.

5. The method of claim 3 in which the ester is the ethyl ester.

6. The method of claim 2 in which T is 'l-thiazolinyl.

7. The methodof claim 6 in which the ester is the methyl ester.

8. A vulcanizable composition comprising a rubber selected from thegroup consisting of natural rubber, polybutadiene, polyisoprene andrubbery copolymers of dienc hydrocarbons with another monomercopolymerizable therewith, sulfur and an ester selected from the groupconsisting of aliphatic esters, aromatic esters, aralkyl esters andcycloaliphatic esters of a compound of the general formula HOOC-Ar-SS-Tin which Ar is an arylene radical and T is selected from the groupconsisting of Z-thiazolyl and 2-thiazolinyl radicals.

9.. A vulcanizable composition comprising a rubber selected from thegroup consisting of natural rubber, polybutadiene, polyisoprene andrubbery copolymcrs of dienc hydrocarbons with another monomercopolymerizablc therewith,, sulfur, and 2-(o-carbomethoxyphenyldithio)-benzothiazole.

10. A vulcanizable composition comprising a rubber selected from thegroup consisting of natural rubber, polybutadiene, polyisoprene andrubbery copolymers of diene hydrocarbons with another monomercopolymerizable therewith, sulfur, and 2-(o-carbethoxyphenyldithio)-benzothiazole.

11. A vulcanizable composition comprising a rubber selected from thegroup consisting of natural rubber, polybutadiene, polyisoprene andrubbery copolymers of diene hydrocarbons with another monomercopolymerizable therewith, sulfur, and 2-(ocarbomethoxyphenyldithio)-thiazoline.

12. A rubber product which has been vulcanized in the presence of anester selected from the group consisting of aliphatic esters, aromaticesters, aralkyl esters and cycloaliphatic esters of a compound of thegeneral formula HOOC-Ar-S-S--T in which Ar is an arylene radical and Tis selected from the group consisting of Z-thiazolyl and 2-thiazolinylradicals.

13. As a new compound Z-(o-carbomethoxyphenyldithio)-benzothiazole.

14. As a new compound 2-(o-carbethoxyphenyldithio)- benzothiazole.

15. As a new compound 2-(o-carbomethoxyphcnyldithio)-thiazoline.

16, As new compounds, the esters of compounds having the general formulaHOOCArS-ST in which Ar is an arylene radical and T is selected from thegroup consisting of Z-thiazolyl and Z-thiazolinyl radicals.

17. As a new compound, an ester of a Z-(carboxyphenyldithiothiazole) 18.As a new compound an ester of a 2-(carboxyphenyldithiothiazoline)References Cited in the file of this patent UNITED STATES PATENTS 6Bargmeyer Feb. 15, 1949 Carr Jan. 12, 1954 Senn Jan. 26, 1954 DArnicoMay 22, 1956 DAmico July 24, 1956 Fields Aug. 28, 1956 Hill Feb. 19,1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION December 30,1958 Patent NOD 2366 778 Richard Leshin It is hereby certified thaterror appears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

column 3 line Column 1 line 49 for "sollution" read me Solution second.column thereof, under the heading Stock Non A for Table 4 "3 .805" read3,850 same Table 2 line 45 fourtlta. column thereof, under the headingStock No 6, for "@850" read we 1 850 mg Signed and. sealed this 5th dayof'May 19590 (SEAL) Attest: V

KARL AXLINE ROBERT c. WATSON Commissioner Of Patents Attesting Oflicer

1. THE METHOD WHICH COMPRISES HEATING A RUBBER SELECTED FROM THE GROUPCONSISTING OF NATURAL RUBBER, POLYBUTADIENE, POLYISOPRENE AND RUBBERYCOPOLYMERS OF DIENE HYDROCARBONS WITH ANOTHER MONOMER COPOLYMERIZABLETHEREWITH AND SULFUR IN THE PRESENCE OF AN ESTER SELECTED FROM THE GROUPCONSISTING OF ALIPHATIC ESTERS, AROMATIC ESTERS ARALKYL ESTERS ANDCYCLOALIPHATIC ESTERS OF A COMPOUND HAVING THE GENERAL FORMULAHOOC-AR-S-S-T IN WHICH AR IS AN ARYLENE RADICAL AND T IS SELECTED FROMTHE GROUP CONSISTING OF 2-THIAZOLYL AND 2-THIAZOLINYL RADICALS.
 13. AS ANEW COMPOUND 2-(O-CARBOMETHYOXYPHENYLDITHIO)-BENZOTHIAZOLE.